A blank font list where? There's no way to get a direct list of fonts: you just try rendering text with a given font and look at the metrics of it versus the fa

A blank font list where? There's no way to get a direct list of fonts: you just try rendering text with a given font and look at the metrics of it versus the fallback. Font lists are done using side-channels (and you also therefore have to have a list of fonts to sniff in the first place). The only way to stop font-based side-channels is to limit the web to a fixed set of fonts: and that will horribly break the web in some linguistic communities where there's a fair amount of web content that relies on specific fonts (that typically map old Windows codespaces to other characters for support for their language, often before Unicode covered those characters). You also need identical fonts for a given user agent, and that's very hard to guarantee short of shipping your own fonts (e.g., consider an OS update that changes a font!), and that becomes expensive fast.